Standby power consumption measurement

[Jeff Layman]

Given up trying to measure this on my LCD TV (egg see
http://www.digitalspy.co.uk/forums/showthread.php?t=757232)

But could someone enlighten me as to how the TV manufacturers do it? What
type of equipment would they use to measure these low consumptions from
power supplies using (very) irregular waveforms?

 

[Don Stauffer]

Given up trying to measure this on my LCD TV (egg see
http://www.digitalspy.co.uk/forums/showthread.php?t=757232)

But could someone enlighten me as to how the TV manufacturers do it? What
type of equipment would they use to measure these low consumptions from
power supplies using (very) irregular waveforms?

I don't think they worry very much about irregular waveforms. I think
they pretty much assume you will be using it on normal power grid. So a
regular wattmeter or equivalent would be okay. Or, an AC ammeter, since
they know the voltage reasonably well.

I also feel my manual will give me a reasonable value- why should they
lie? My manual indicated my LCD TV has a negligible consumption when
off, not the monster drains that some news broadcasts have touted.

 

[Jeff Layman]

I don't think they worry very much about irregular waveforms. I think
they pretty much assume you will be using it on normal power grid. So a
regular wattmeter or equivalent would be okay. Or, an AC ammeter, since
they know the voltage reasonably well.

I also feel my manual will give me a reasonable value- why should they
lie? My manual indicated my LCD TV has a negligible consumption when
off, not the monster drains that some news broadcasts have touted.

According to the forum thread I quoted, ordinary instruments do not give an
accurate measurement of power consumption with standby power levels. I
don't understand the technicalities (power factors, pulsed voltages, etc) as
they seems to give pretty accurate readings when the TVs are operating
normally.

And as to the figure quoted in the manual, not everything is as it seems ;-)
http://arstechnica.com/gadgets/news/2009/02/sony-lcd-exceeds-energy-star-power-draw-75-of-time.ars

 

[Eeyore]

Given up trying to measure this on my LCD TV (egg see
http://www.digitalspy.co.uk/forums/showthread.php?t=757232)

But could someone enlighten me as to how the TV manufacturers do it? What
type of equipment would they use to measure these low consumptions from
power supplies using (very) irregular waveforms?

Things called true power meters.

Graham

 

[Eeyore]

Or, an AC ammeter, since they know the voltage reasonably well.

That would give you VA ( apparent power ) NOT true watts. Please don't post
about things you don't understand.
http://en.wikipedia.org/wiki/Apparent_power
http://en.wikipedia.org/wiki/Power_factor_correction
http://en.wikipedia.org/wiki/Active_power_factor_correction#Active_PFC

Graham

 

[Eeyore]

According to the forum thread I quoted, ordinary instruments do not give an
accurate measurement of power consumption with standby power levels.

Or operating quite often too.

Read my reply.

Graham

 

[News123]

And as to the figure quoted in the manual, not everything is as it seems ;-)
http://arstechnica.com/gadgets/news/2009/02/sony-lcd-exceeds-energy-star-power-draw-75-of-time.ars

What I consider strange is:
Though I agree with:

This is a problem Sony should've found and fixed before the televisions hit the market—if a TV is spending 75 percent of its time in update mode consuming 20W, one expects someone on the testing floor should have noticed.

I must say, that it's not only Sony's fault.
If the government distributes 'Energy Star' stickers, then they should
have cwertification / measuring techniques, which capture such issues.
As more and more devices are doing things like auto updates and other
nanny work while officially being switched off, they might have to
increase the time, they take for measuring.

 

[Eeyore]

I must say, that it's not only Sony's fault.
If the government distributes 'Energy Star' stickers, then they should
have cwertification / measuring techniques, which capture such issues.
As more and more devices are doing things like auto updates and other
nanny work while officially being switched off, they might have to
increase the time, they take for measuring.

Standby power consumption is increasingly having limits mandated by the IEC ( International Electrotechnical Commission ). Having standards that only apply in one country is rather silly.

The current goal AIUI is to get consumer goods down to 1W in standby. That's not ratified yet. Instead we have silly set-top boxes like the one supplied by my cable co that apparently does nothing other than blank the display
when put in standy and consumes the same power more or less.

My CRT monitor does drop to 3W in standby though ( Sony 21" E530 ) which I reckon is pretty good. 130W active.

Graham

 

[Don Stauffer]

That would give you VA ( apparent power ) NOT true watts. Please don't post
about things you don't understand.
http://en.wikipedia.org/wiki/Apparent_power
http://en.wikipedia.org/wiki/Power_factor_correction
http://en.wikipedia.org/wiki/Active_power_factor_correction#Active_PFC

Graham

But how much of a power factor does a modern piece of electronics have?
Yeah, a motor or something with a very large inductor has a lot, but
from what I have seen from the guts of modern heavy IC electronics,
there isn't much in there to create a big power factor. No big
deflection coils and stuff like that any more. Big enormous filter caps
seem to have disappeared.

 

[Jeff Layman]

Things called true power meters.

Graham

Thanks.

But Google not much help here - only 39 hits for "true power meter", and
many of those completely irrelevant.

Found one link which led to a Fluke 43B, but that cannot go down to 0.3w.
Most of the relevant refs were for higher power measurement (eg those which
could check house electricity meters). Other delving for lower power
instruments only turned up those for RF power measurement.

Could you point me in the direction of an instrument which measures powers
below 1w at 50Hz, or suggest other suitable search terms?

TIA

 

[Ken]

But how much of a power factor does a modern piece of electronics have?

0.60